MICROPROPAGATION OF PEAR, PYRUS COMMUNIS L., IN A DOUBLE-PHASE CULTURE MEDIUM

Pear, cultivars "Durondeau", "Conférence", "Doyenné du Comice" and "Professeur Molon", was micropropagated by a technique combining a liquid and an agar-solidified phase.

Compared to agar-solidified medium, production of microcuttings was improved by this technique in terms of quality and yield. Results were affected by the agar concentration in the solidified phase and by the volume of the additional liquid medium.

The double-phase technique gave high yield of axillary shoots, while avoiding vitrification. The average number of axillary shoots with cultivar "Durondeau" reached 6–7 on this medium after six subcultures, compared to 2–3 for a classical medium containing 0,5 % agar.

A rise in pH was always observed with the double-phase medium at the end of the culture cycle, irrespective of the initial pH (4.8, 5.5 or 6.2), while pH decreased with the agar-solidified medium.